RE: [stella] Ms. Pac Man, Mr. Do, striped playfields, and one-line kernels

Subject: RE: [stella] Ms. Pac Man, Mr. Do, striped playfields, and one-line kernels
From: "Lee Fastenau" <stella@xxxxxxxxxxxxxxx>
Date: Wed, 1 Sep 2004 22:16:44 -0500
> Hi Lee,
> > I was able to get around using skipdraw by page-aligning my sprites and
> > padding the top (remember, it's stored upside down) with zeroes
> to fill up
> > the page.
> I'm curious if skipDraw wouldn't help reduce the need for that sprite
> padding. Did you post the lastest source to [stella]?

Skipdraw would eliminate the need for padding, but I don't believe I have
enough free cycles for it in my kernel.  Basically, I have 14 cycles free to
set up my ball sprite before some other time-critical stuff starts
happening... and that's counting 2 cycles at the end of the previous

Thomas's 9-cycle skipdraw would still need an additional 7 cycles to set the
sprite, which puts me over budget.  I've never used skipdraw, so maybe I'm
looking at it wrong. :)  14 cycles seems like a lot though, especially since
I removed the ball highlight and have plugged the gap with a "SLEEP 7".  If
you can see a way to do it in my code, please let me know.  (Search for
"gameArea" in the source to find the game kernel.)

> Did you try aligning your sprites at an offset the same as the kernel
> height and using y as a scan line counter?

I think the page-size sprite trick is an all-or-nothing deal.  It would make
sense to only have as much padding as you have kernel scanlines, but without
some sort of skipdraw-ish routine in your kernel, the sprite offset value
would merrily venture into non-sprite ROM!  At that point, you may as well
go with the more ROM-friendly skipdraw routine.

> Take care,
> Dennis


PS: I'm not hurting for ROM space right now, but I'm ALWAYS interested in
optimizing my code, so any suggestions are appreciated.  Please note that
I'm in the middle of beefing up ball speed/direction logic, so while it's
playable, it's not yet nearly as challenging as it will one day be. :)
Also, the music is a placeholder (my interpretation of a tune from an Amiga
"intro" called Lost in Legoland by Andromeda).  Umm... and lots of other
excuses and caveats.

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